End of unit
1The diagram shows a simplified flow diagram of a water treatment works which supplies drinking water.
aiWhat is the purpose of filtration?
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iiWhat is the purpose of chlorination?
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bSamples of the treated water must be tested at regular intervals. Suggest one reason why.
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cIn some parts of the country the water supplied to homes is hard water.
iName one ion that can make water hard.
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iiExplain how hard water can affect central heating systems.
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iiiState one advantage of hard water.
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AQA, 2007
2Ethanol can be used as a fuel. The equation for the combustion of ethanol is:
CH3CH2OH + 3O2→ 2CO2 + 3H2O
Use the energy level diagram to help you answer these questions.
aHow can you tell from the diagram that this reaction is exothermic?
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bCopy the diagram and draw a line to show what happens if a catalyst is used.
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cWhat is the effect of a catalyst on the overall energy change for the reaction?
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The student decided to calculate the energy change using bond energies. He wrote this equation to help.
He looked up the following bond energies.
Bond / Bond energy in kJ per mole / Bond / Bond energy in kJ per moleC–H / 413 / O–H / 464
C–C / 347 / O=O / 498
C–O / 336 / C=O / 805
dCalculate the energy needed to break the bonds in the reactants.
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eCalculate the energy released when the bonds in the products are formed.
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fCalculate the energy change for the reaction.
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gCalculate the energy change in joules per g of ethanol.
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3Some chemical tests were done on solutions of four substances, A, B, C and D. The table shows the tests and the results of the tests.
Substance / Flame test colour / Sodium hydroxide solution added / Nitric acid and silver nitrate solution added / Hydrochloric acid and barium chloride addedA / No colour / White precipitate that dissolves in excess sodium hydroxide / No reaction / White precipitate
B / Lilac / No reaction / Cream precipitate / No reaction
C / Crimson / No reaction / White precipitate / No reaction
D / No colour / Green precipitate / No reaction / White precipitate
Name the four substances:
A …………………………………………………
B …………………………………………………
C …………………………………………………
D …………………………………………………(8)
4When compound X with the formula CH3COOCH2CH3 is heated with dilute hydrochloric acid it reacts with water. Two compounds Y and Z are produced. The equation for the reaction is:
CH3COOCH2CH3 + H2O → CH3COOH + CH3CH2OH
XYZ
aName compounds X, Y and Z.
X …………………………………………………
Y …………………………………………………
Z …………………………………………………(3)
bFor each of X, Y and Z, name the group of organic compounds to which it belongs.
X …………………………………………………
Y …………………………………………………
Z …………………………………………………(3)
cY and Z can be separated by distillation. They are both colourless liquids. Describe a simple test that you could use to distinguish between Y and Z. Give the results of the test for both Y and Z.
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5In this question you will be assessed for using good English, organising information clearly and using specialist terms where appropriate.
Ammonia is produced by the Haber process. In the process nitrogen and hydrogen are mixed. The pressure is increased to about 200 atmospheres. The gases are passed over an iron catalyst at about 450°C. The equation for the reaction is:
N2(g) + 3H2(g) 2NH3(g)
The reaction between nitrogen and hydrogen is reversible. This affects the amount of ammonia that it is possible to obtain from the process. The graph shows how the pressure and temperature affect the percentage of ammonia that can be produced.
Use this information, together with your knowledge of the process, to explain why many industrial ammonia plants operate at 200 atmospheres and 450 °C.
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AQA, 2006
© Oxford University Press 2014
This resource sheet may have been changed from the original.
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